Electron gun having electrode cup in ceramic cavity



July 1, '1969 F. G. OESS 3,453,473

ELECTRON GUN HAVING ELECTRODE CUP IN CERAMIC CAVITY Filed Jan. 2, 1968 Frederick G. Oess,

INVENTOR.

ATTORNEY.

United States Patent Office 3,453,473 Patented July 1, 1969 3,453,473 ELECTRON GUN HAVING ELECTRODE CUP IN CERAMIC CAVITY Frederick G. Oess, Oceanside, Calif., assignor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed Jan. 2, 1968, Ser. No. 694,943 Int. Cl. H01j 29/48 US. Cl. 313-82 3 Claims ABSTRACT OF THE DISCLOSURE The electrode structure comprises a metallic cup telescopically received in a cavitied ceramic and telescopically receiving an inner ceramic washer. The cup is indented on its side wall and compression plugs are fitted in the indentations to provide a force fit between the cup and ceramic insulators.

The invention relates to an electrode structure for use in an electron gun and the method of manufacture thereof.

Electron guns as used, for example, in cathode ray tubes may be provided with one or more control electrodes to modulate the electron beam from a full off position to a maximum electron beam flow. Control of electrodes of this type are commonly known as grids and are sometimes denominated G1, especially where the control electrode is positioned immediately forwardly of the electron producing cathode and used to regulate the flow of the electrons therefrom. To properly function a G1 control electrode must be electrically isolated from adjacent structure, hence, must be physically mounted within the gun via insulators. In normal electron gun environment thermal energy, that is, heat is used to create electron flow from the cathode. Thus, it will be understood that the environmental temperature condition of the control electrode varies greatly in time. This temperature variation creates different degrees of expansion and contraction of various parts of the electrode structure due to the varying composition, that is, metal and ceramic. An all too frequent result that characterized prior art control grid structures in their operational sites is that the expan sion and contraction resulted in a failure to maintain physical integrity and consequent misalignment of the control grid with other operating parts of the electron gun. There followed faulty electron gun functioning and below par operation of the equipment with which the electron gun was associated, for example, a cathode ray tube.

A primary object of the invention is to provide a control electrode of the type described having a structure adapted to maintain its physical integrity in operational sites.

It is a further object of the invention to provide control electrodes of the type described which utilize a novel interference fit relationship between its structural parts to maintain physical integrity therebetween.

It is a further object of the invention to provide a unique method of assembly of the control electrode of the type described.

These and other features and advantages of the invention will become apparent in the course of the following description and from an examination of the related drawings, wherein:

FIGURE 1 is a central vertical sectional view of a control grid and its components prior to assembly, illustrating the relationship of the parts;

FIG. 1A is a sectional view taken along lines 1A--1A of FIG. 1;

FIG. 2 is a side elevational view, partially in section, of a step in the final manufacture of the control grid;

FIG. 2A is a sectional view taken along lines 2A-2A of FIG. 2;

FIG. 3 is a side elevational view, partially in section, of an assembled control grid;

FIG. 3A is a sectional view taken along line 3A3A of FIG. 3; and

FIGS. 4 and 4A are detail views of a typical metallic cup employed in the invention.

Describing the invention in detail, attention is directed to FIGS. 1 and 1A. A typical control electrode comprises essentially three components, namely, a metallic cup indicated by the numeral 10 which usually is a drawn metallic element having an electron beam aperture 12 centrally located in its lower wall aspect. As is well known to those familiar with this art, cup 10 is normally positioned in the electron gun with the aperture 12 in alignment with an electron producing cathode, the aperture 12 providing an escape opening for the electron beam in the completed gun.

The internal cavity 14 of the cup 10 receives an annular insulating element 16 and the cup 10 is telescopically received Within a cavity 18 and an outer insulating element 20. In the pre-assembled condition illustrated in FIGS. 1 and 1A, the inner insulating element 16 is loosely received Within the cavity 14 of the cup 10 while the cup 10 per se is loosely received within the cavity 18 formed in outer insulating element 20.

In an initial step in the fabrication of the typical control electrode, the cup 10 is subjected to an indentation operation, as is shown in FIGS. 4 and 4A. The outer peripheral wall 15 of the cup 10 is indented as at 22, 22. The indentations are forced inwardly to a degree which results in an interference fit with the outer diameter of the inner insulating element 16. In a typical control electrode having a cup 10 With an approximate diameter of three-quarters of an inch, indentations 22 may be arcuate on a three-quarter inch radius and can be formed to provide an interference fit with the outer diameter of inner insulating element 16 of approximately twoto threethousandths of an inch. Such a fit has been found satisfactory. Additionally, three indentations 22, spaced degrees apart, are suggested in a cup of the dimension mentioned although it will be understood that any number of indentations may be used and a different degree of interference fit provided, depending upon the physical size of the components.

Attention is now directed to FIGS. 2 and 2A which show the cup 10, in its indented condition, telescopically received within the cavity 18 of outer insulating element 20. As seen in FIG. 2A, slightly enlarged receiving cavities 26 are defined in the areas of indentation 22 between the surfaces thereof and the adjacent surface of cavity 18 of the outer insulating element 20. The next step in electrode assembly involves the positioning of compression plugs 28, 28 in respective cavities 26 and generally parallel to the long axis of the cup 10. In a preferred practice of the invention the compression plugs 28 should have certain physical characteristics. For example, they should be softer than the grid cup material and should be sufiiciently soft and ductile to conform to any irregularities which may exist in the inner diameter surface of the outer insulating element 20. For example, and if desired, the inner diameter surface of the outer insulating element 20 can be serrated to provide such irregularities and receive the soft compression plugs during the final assembly steps hereinafter described. Also, the compression plug material must be able to physically withstand application situs temperatures up to 700 C. without deforming. It also should be hard enough to avoid becoming loose under shock and vibration. In a preferred embodiment of the invention, and utilizing the cup dimensionally described above, gold wire of a nomi- 3 nal ten-thousandths of an inch in diameter, preflattened as shown in FIG. 2A, has been found satisfactory.

FIGS. 3 and 3A illustrate the final assembled configuration of a typical control electrode and also illustrate the final assembly operation. With the parts positioned as shown in FIG. 2, that is, a relatively loose assembly of the cup 10, outer insulating element 20 and compression plugs 28, the inner insulating element 16 is telescopically deposited in the cavity 14 of the cup 10. As noted, the indentations 22 are in interference relationship with outer diameter of the inner insulating element 16. Assembly of the inner insulating element 16, therefore, requires force fitting the element 16 downwardly as shown by arrow 30 in FIG. 3. This force fit distorts each segment 22 outwardly, compressing and flattening related plugs 28 and providing a tight pressure fit between the respective components of the control grid, namely, the outer insulating element 20, the inner insulating element 16, and the cup 10. The points of presure fit are clearly shown at 32 in FIG. 3A.

It is characteristic that the complete structure provided is relatively free from stress distortions of prior art electrode structures which, for example, used spot welding techniques to accomplish the assembly.

In a preferred embodiment of the invention the grid cup 10 may be fabricated from type 305 stainless steel and the inner and outer insulating elements 16 and 20 formed of conventional ceramic. As shown, the metallic cup 10 is free to expand and contract under temperature variations throughout a major segment of its physical structure independently of the expansion or contraction of the related ceramics because contact is limited to small localized compression areas. Thus, a physical integrity of the entire assembled electrode application can be and has been anticipated.

It will also be apparent that the novel assembly method described is uniquely adapted to provide such a distortion-free control electrode structure.

The invention as shown is by way of illustration and not limitation and may be subject to modification, all within the scope of the dependent claims and the specification.

What is claimed is:

1. An electron gun comprising an annular insulating element having a central cavity therein, an electrode cup disposed in the cavity, a second insulating element telescopically disposed in the cup, said cup having deformed areas in its outer wall, said deformed areas providing an interfering fit with the second element disposed in the cup, and compression plugs interposed between the cup and the cavity surface of the first element, said compression plugs being pressure fitted between the cup wall and the outer element as a result of the pressure fit between the deformed area and the second element.

2. An electron gun according to claim 1, wherein the compression plugs comprise a soft ductile material plastically deformed between the cup and the cavity surface.

3. An electron gun according to claim 2 wherein the cup is deformed in 3 areas and said compression plugs comprise gold wire.

References Cited UNITED STATES PATENTS 3,210,145 10/1965 Fyler 31382 X 3,247,410 4/1966 Oess 31382 X 3,320,457 5/1967 Burdick et al. 313-82 ROBERT SEGAL, Primary Examiner.

U.S.Cl.X.R. 3 l3-83, 292 

